为什么我这个程序size一直是1，接收一段数据只能读取到前面两个

/*
 * Copyright (c) 2006-2021, RT-Thread Development Team
 *
 * SPDX-License-Identifier: Apache-2.0
 *
 * Change Logs:
 * Date           Author       Notes
 * 2021-10-26     RT-Thread    first version
 */
#include <rtthread.h>
#include"rtdevice.h"
#define DBG_TAG "main"
#define DBG_LVL DBG_LOG
#include <rtdbg.h>
static rt_err_t uart1_input(rt_device_t dev,rt_size_t size)
{
    LOG_D("触发中断");
    char c;
    int i;
    for(i=0;i<size;i++)
    {
        rt_device_read(dev, 0, &c, 1);
        LOG_D(":%d",size);
    }
    return RT_EOK;
}
int main(void)
{
    rt_device_t uart=rt_device_find("uart1");
    rt_device_open(uart, RT_DEVICE_FLAG_INT_RX);
    rt_device_set_rx_indicate(uart, uart1_input);
    return RT_EOK;
}